Turbine plant accessories, such as air turbine starters (ATS) may be mounted to a jet engine through a gearbox or other transmission assembly. These accessories typically require lubrication to operate properly. In the case of an ATS, an assisted wet cavity (AWC) design has been employed in the past to assist in supplying lubrication to the ATS. These designs include an ATS housing having a mounting face or mounting flange that is sealingly engaged with, and coupled to, the gearbox to define a porting system. The porting system allows transfer of lubricating oil between the gearbox and the starter via a “make up system”, i.e., during normal operation, lubricating oil first is provided to the gearbox and may be transferred to the starter if the starter lubricant quantity is below a specific level. The lubricating oil may enter a port in the porting system that is typically in fluid communication with passages within the starter housing and may or may not be distributed to the starter.
Although AWC designs are generally effective, they have certain drawbacks. Additionally, typically the gearbox and accessory are at a pressure above ambient pressure. In the highly unlikely event of a starter housing breach and a change in pressure, the starter pressure may drop to equalize with ambient pressure, which may result in a relatively small pressure difference between the starter housing and gearbox of about 0.1-0.3 psi.
Though this pressure differential may be relatively small, excessive lubricating oil, which is fed from the gearbox to the accessory in an AWC design, may leak from the gearbox to the starter and, consequently, out through the breach. Although generally a check or reed valve has been used to counteract the potential oil loss, it has been found that because the pressure differential between the starter and gearbox can be small, these check valves may not work consistently.
Accordingly, there is a need for a lubrication system capable of providing a metered fluid flow between a turbine plant accessory and a gearbox assembly. There is also a need for a system having improved fluid flow control in the unlikely event of an accessory housing breach. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.